The present invention relates to copying machines in general, especially to projection printers, and more particularly to improvements in apparatus for applying markers to intermittently or continuously moving webs of photographic material in a copying machine. Still more particularly, the invention relates to improvements in apparatus which are utilized to apply markers denoting the locations where a web of photographic material must be severed to yield discrete prints as well as markers which denote the last print of a series of associated prints, especially the last print of a series or group of prints belonging to a given customer.
In accordance with a presently known technique, the copying machine comprises an apparatus for exposing suitable (readily detectable) markers onto the photosensitive layer of a photographic paper web. The markers are normally applied to one of the longitudinally extending marginal portions of the web, i.e., adjacent to one side of the row of exposed images on the photosensitive layer. When the web has been transported through the developing apparatus, it is severed at intervals in response to detection of successive markers so as to be converted into a series of discrete prints. The severing operation normally or often involves separation of that marginal portion which is provided with the markers. The markers are detected by a photoelectric scanning device which transmits signals to the severing device and to the means for transporting the web lengthwise. Reference may be had to German Offenlegungsschrift No. 2,141,950.
It is also known to provide a web of photographic material with markers in the form of slits, cutouts or notches, preferably slits which are formed in the frame lines between successive latent images on the web. As a rule, a slit is formed in the frame line behind the last exposed image, i.e., in the narrow space between the freshly exposed image and the area about to be exposed to light which passes through the next-following frame of an exposed and developed photographic film. The marker (preferably a slit) which denotes the last print of an order is also formed in a frame line adjacent to and in line with the slit which identifies an image. When the web has passed through the developing machine, the slits denoting successive images and the slits denoting the last prints of successive orders are detected by discrete photoelectric monitoring devices one of which transmits signals to the severing means and to the means for transporting the exposed and developed web, and the other of which transmits signals to suitable apparatus which assemble the prints of an order, introduce the assembled prints into envelopes, and insert into the envelopes the corresponding portions of photographic film so that the envelopes can be returned to the dealers (who accepted the orders from customers) or directly to the customers. The severing device is preferably designed to remove from the web narrow strips of photographic paper, and each such strip contains a marker (slit) which denotes the respective print, or a first marker which denotes the respective print and a second marker (slit) which denotes the last print of the respective order.
The making of slit-shaped markers in the frame lines rather than in the marginal portions of a photographic paper web is desirable and advantageous because the web is less likely to break (i.e., it is weakened to a lesser extent if the slits are remote from its marginal portions). On the other hand, the markers which are exposed onto the photosensitive layer of the web are preferably applied to one of the marginal portions because they can be readily removed by the simple expedient of severing or trimming the web in such a way that the respective marginal portion is separated from the prints. The making of exposed markers in the marginal portions of a web is desirable on the additional ground that it would be difficult or impossible to detect a marker which has been exposed into the frame line between two partially overlapping neighboring latent images. On the other hand, a marker in the form of a slit or cutout which is provided in the frame line between two neighboring images can be detected irrespective of whether or not such images overlap.
Markers in the form of exposed dots or other configurations in one marginal portion of the web are normally resorted to if the prints are provided with margins surrounding two or more sides of the image. Markers in the form of slits are preferred when the web is to be subdivided into margin-free prints. Such procedures are desirable in order to achieve savings in photographic paper. However, it is nevertheless desirable to design the marker applying apparatus of a photographic copying machine in such a way that markers in the form of exposed dots or other configurations on the photosensitive layer of the web can be applied to the frame lines between neighboring images. Such technique can be resorted to when the photoelectric or other monitoring means of the copying machine is designed or positioned to detect markers which are remote from the marginal portions of the web, i.e., which are provided in the frame lines.
As a rule, signals for the making of markers are electric signals which are produced at an appropriate time in the course of each copying cycle. The application of markers which denote successive prints presents no problems because such markers can be applied to the web during exposure of the corresponding film frames on the original. On the other hand, the application of markers which denote the last print of an order is more difficult, primarily because the monitoring device cannot or should not be placed into immediate proximity of the severing device. Thus, it happens frequently that the space which is available in a copying machine for the installation of monitoring device is remote from the severing device so that the monitoring device detects markers denoting the last prints of successive orders well ahead of the severing station. This means that the copying machine must be provided with a storage or time delay device which delays the transmission of signals denoting the last prints of successive orders for periods of time corresponding to those which are needed to actuate the severing device two, three, four or more times before the last print of an order is separated from the next-following portion of the web. In most instances, the storage includes an electrical or electronic time delay device. A drawback of such storages is that they fail to operate properly when the connection to the source of electrical energy is interrupted or in the event of malfunction, i.e., the signal which is to denote the last print of an order is likely to be lost or is generated prematurely or too late. This can result in a complete breakdown of the automatic print gathering and processing operation, i.e., the prints are not assembled into groups which belong to given customers so that the customers or dealers receive prints belonging to other customers or dealers.